In yesterday's Eureka, our heroes discover someone in town might have been in league with Beverly Barlowe's nefarious consortium. The hunt to unmask the mole wasn't exactly Tinker, Tailor, Soldier, Spy… but it was one of the season's best episodes.

Some pretty major spoilers ahead…

"The Honeymooners" finds Jack and Allison finally going on their well-deserved honeymoon. Unbeknownst to his new bride, Carter decided they should spend their honeymoon in a dilapidated cabin belong to his predecessor, Sheriff Cobb. It's all an attempt to put down roots and build a marriage that will really last, but all their getaway accomplishes is a lot of rustic misery -– and the discovery of a secret investigation Sheriff Cobb was undertaking years ago. He knew there were spies in Eureka, the long-since-revealed Beverly Barlowe was just the tip of the iceberg, and he left an ancient optical disc that might hold the identity of the other spies.

Jo and Deputy Andy take up the case, and to all appearances, they are the worst spyhunters in the world. Andy loudly blabs that they are looking for a spy to anyone who will listen, so overtaken with the glee of the big investigation. They make no attempt to swear people to secrecy, they discuss their plans in public, they let town blabbermouth Vince find out about everything. Jo and Andy, I knew George Smiley, I've read books about George Smiley, I've watched Gary Oldman play George Smiley -– and you two are no George Smiley.

Except, of course, somewhere along the way, the incompetence turns back into brilliance, as Jo secretly enlists Vince to tell everyone what's going on in an effort to flush out the spy by making him or her go steal the disc. This probably only works if the mole in question assumes Jo and Andy are too dumb to place the disc under surveillance, but hey, it made for a nice little twist. And Jo's little gambit leads to the next shocking turn, as Henry's wife Grace outs herself as one of Beverly's spies. But she is protecting a still greater secret: the person between her and Beverly was Henry, specifically the version of him that once existed in this timeline.

In the midst of all the spycatching fun, Fargo and Zane are busy trying to save Holly. Her brain has been transferred to a freshly printed – yes, printed – body, but something is wrong in her mind. She becomes convinced that she is still stuck in virtual reality, and the walls between what's real and what's fake begin to crumble, particularly when she suddenly remembers it was the virtual Carter who killed her in the last simulation. It's the latest brutal turn for Holly's journey home, and if the resolution is a little easy –- Zane manages to "reboot" her degrading brain, and she's fine again –- at least the episode puts the characters through enough that you want them to have something go their way, just this once.

This is one of the most packed episodes of Eureka I can remember, which is all the more remarkable when the first half is mostly given over to Allison and Jack's honeymoon ordeal. This is probably the least interesting part of the episode, and the mix of relationship drama and cabin-destroying slapstick comedy doesn't quite gel together, but it's another nice examination of the challenges Allison and Jack face as a couple, and why they are ultimately going to make it all work out. Plus, it helps underscore the theme of people doing everything they can for those they love. Allison namechecks Fargo's devotion to Holly, and Henry's devastation at what Grace has done –- but as we find out, it's actually Grace who is arguably making the greatest sacrifice for love.

The revelation about alternate Henry, in which a character learns his old timeline self did something he finds abhorrent, is something for which I've been agitating for some time now, because it always struck me as the most thematically rich implication of the timeline shift. There are a few potential plot holes the show is going to have to navigate to make this work — the big one being why Beverly kept trying to recruit him when in this timeline, he was working with her all along. Of course, there's a pretty obvious solution to that, but it's a heartbreaker -– once Grace learned the truth, she told Beverly. This might actually also explain how Beverly came to approach James Callis's Dr. Grant back in season 4.0, but I'm going to leave it to another day to tease out the full implications of this big reveal.

Part of what I love about this reveal is how it potentially gets Eureka out of its continuity problem. The show rebooted with the timeline shift, but by then it had already quietly jettisoned a lot of the more overly complicated aspects of the earlier seasons –- the Artifact is the obvious example here, but the death of Henry's first love Kim and his time traveling to keep her alive also kind of fell by the wayside. Since Kim's death was the main reason Henry hated Beverly in the first place, the fact that the show had moved so far away from those events made their interactions in recent seasons a bit weird, as the writers always seemed to dance around just what exactly was Henry's problem with Beverly. This revelation potentially recasts Henry and Beverly's relationship very much in terms of the timeline shift, and it means each holds the other responsible for things that didn't quite happen the same way in the other timeline. That's a bit confusing, yes, but I'm hoping the show can run with these ideas a bit further as we head to the grand finale.

More fundamentally, alternate Henry's treachery is fascinating on a character level. As Beverly pointed out to him on multiple occasions –- and now we have a better idea why she kept bringing this up –- Henry shared many of the same concerns the Consortium had about Eureka, and he's repeatedly shown a willingness to bend or even break the rules if he's doing what he believes is right. It's not hard to see how Henry could indeed have allied himself with Beverly if things had shaken out differently -– if, say, the circumstances of Kim's death had been different, and Beverly hadn't been implicated. The timeline shift always had the potential to cast a dark shadow on just what our heroes are capable of under the right circumstances, and idea the show developed earlier this season with the virtual reality episodes, and I'm excited that they're exploring this fertile territory before the end.

Also, credit where it's due — Eureka pulled off a few legitimately nice reversals this episode. I can't say I was exactly shocked when the Grace and the Henry reveals came, since the traitor really had to be someone major, and it would make sense for a character actually involved in that subplot to end up being the traitor, which immediately narrowed things down to Vince, Grace, Henry, and technically Jo. But the show did a nice job of first casting suspicions on Vince, then doing just enough to make you think Grace is the traitor before the really big twist that it was Henry all along.

Overall, this episode was pretty much a triumph, overcoming a slightly slow start to deliver three very satisfying and very different stories. While Henry and Grace's story dominated this recap, the Holly stuff was great, and again gave some great material for Felicia Day, Neil Grayston, and Niall Matter. The show has arguably strung out Holly's resurrection a bit longer than it absolutely had to, but they are trying to bring someone back from the dead here –- I can see how that might keep throwing up pitfalls like this. And Holly's big confrontation with Carter and her subsequent tearful breakdown may well have been Day's finest moment on the show. If the show can keep this kind of quality up over its final few episodes, we are headed for one hell of a finale.